In chemical sprayers, for example agricultural sprayers, relatively long spray booms extend outwardly on each side of the centre of a trailer or other vehicle. The booms carry spaced spray nozzles and chemical supply lines connecting them to a pump that is carried on the vehicle together with all the necessary conventional equipment to eject liquid from the spray nozzles.
Conventionally, height adjustment is by rotating the boom carrier, which raises and lowers the spray boom in an arc. The main disadvantages of this arrangement are that as the spray boom is raised and lowered, the orientation of the spray nozzles changes, and that the maximum height is limited by the length of the arms extending between the spray boom and the boom carrier. The present invention aims at the amelioration of these disadvantages.